The present invention relates to slip forms for concrete walls and is concerned, more particularly, with slip forms for curved walls such as chimneys or smokestacks.
Such slip forms typically are supported on the finished or "set" portion of the wall and are moved upwardly therewith as the wall progresses. The two sides of the form are tied together across the wall close to the pouring level and, with curved walls, the respective sides are trussed into the desired arc by means of longitudinally adjustable trusses.
However, certain problems have been encountered, particularly regarding the adjustment of the diameter of the form surfaces to produce the desired diameter of poured wall.
This is particularly true in the case of circular structures, such as stacks, in which accuracy of form placement requires expensive equipment and considerable effort in adjusting, checking and readjusting. All of this is further compounded if the stack is to be formed with an upward taper.
Furthermore, prior slip forms are unsuitable for structures which are to flare upwardly and thus increase in cross-section as the height increases.
Therefore, prior slip form have not been found to be entirely satisfactory.